JPS627146B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is a rigid inorganic foam prill.
The present invention relates to inorganic foam prills, and in particular to such foam prills composed of layer minerals. In particular, the present invention has a cell structure (a
The present invention relates to a hard inorganic foam prill having a cellular structure and composed of one or more layered minerals, and a method for producing the same. The rigid inorganic foam prills of the present invention are useful as intermediates for the production of inorganic foam products. BACKGROUND OF THE INVENTION Layered minerals are a naturally occurring form of silica and are phyllosilicate materials, ie, have a layered structure. The term “layered mineral” includes:
Examples include vermiculite, kaolinite and other clay minerals, montmorillonite, sepiolite, attapulgite, illite and saponite. Clay minerals exist in clay as particles on the order of a few microns in diameter, and these particles are aggregates or aggregates of small crystal units with submicron dimensions. Kaolin-type clays are essentially a collection of book-shaped units of sheets of the clay mineral kaolinite. The term “kaolinite” is
As used herein, clays that are not composed of pure kaolinite but substantially contain kaolin minerals are intended to be included, such as kaolin-type clays, ball clays, fireclays, china clays, and the like. For example, fireclay is a mixture of kaolinite and illite. Layered minerals are well known and at least some are widely used in industry. Kaolinite and kaolin-containing clays are widely used in a number of industries, including primarily in the ceramic industry for the production of whiteware, porcelain and refractories, and for paper, paints, adhesives, plastics and rubber. It is used as a filler.
Vermiculite is commonly used in heat-exfoliated form (exfoliated vermiculite) as an insulating material in the loose-file and in bonded form as slab or board material for insulation and fire protection. It is used for commercial and agricultural purposes. On the other hand, delaminated
Vermiculite - by which we mean vermiculite which must be delaminated by a chemical treatment followed by swelling in water and a grinding or grinding process - for use in the production of sheet materials or paper and It has already been proposed as a coating for supports (substrates) and for the production of rigid inorganic foam products used for insulation and fire protection. Rigid foams of delaminated vermiculite and their uses are described, for example, in the applicant's own US Pat. No. 4,130,687, according to which cellular structures composed of lamellae of vermiculite are The rigid foam, consisting of a cellular structure, forms a suspension of vermiculite lamellae in a liquid medium, generates gas in this suspension to form a foam, and removes the liquid medium from the foam formed. It is produced by a method consisting of removal by evaporation. Montmorillonite is widely used industrially as a filler for paper, paints and adhesives. Sepiolite is widely used in the ceramic industry. Hard materials made from kaolinite, such as whiteware, porcelain and refractories, are dense, brittle materials produced by various methods involving firing or sintering operations. Although kaolinite itself is a poor thermal conductor, the dense hard materials traditionally made from kaolinite do not exhibit good insulating properties. Products made from kaolin-containing clays are dense (and therefore heavy), brittle, and have only moderate insulating properties, so they are not commonly used for thermal insulation or fire protection purposes.
Hard materials made from heat-exfoliated vermiculite are dense (heavy) and rather brittle materials, so they are used industrially for fire protection in structural steel members, but they are also used for insulation purposes. It is not used much for any purpose. Rigid foam materials made from delaminated vermiculite, unlike their heat-exfoliated counterparts, are lightweight and exhibit good fire protection and insulation properties; It is difficult to manufacture such materials. Such rigid foam materials tend to crack and deform significantly when drying;
It is difficult to manufacture these in the form of slabs or boards larger than about 30 cm square and 3 cm thick. Means, action, and effect for solving the problems The present inventors have recently developed a low-density product made of layered mineral that is lightweight and exhibits good thermal insulation and fire retardant properties, for example, 3 m x 1 m x 10 cm (thickness). A new prill of rigid inorganic foam with a cellular structure of one or more layered minerals has been produced which is useful as an intermediate which can be readily produced in the form of slabs or boards of dimensions up to . Accordingly, the present invention provides a prill of rigid inorganic foam having a cellular structure and composed of one or more layered minerals. As used throughout this specification, the term "prills" is not intended to imply any particular size, shape or structure for each individual piece of foam; means a particle, bead, piece or nodule of a foam having a cell wall composed of layered mineral particles or particles. For example, and just as a guide, a prill is a cylindrical or essentially spherical piece of foam having a maximum dimension of about 5 mm or less, such as from 0.5 to 5 mm. The term "rigid foam" as used for the prills of the present invention refers to a material with structural integrity that is a two-phase dispersion of gas in a solid matrix with an essentially open cell structure. Similarly, the term "rigid inorganic foam" refers to a layered mineral containing a small amount of an organic By this we mean a rigid foam formed essentially of inorganic material, although the presence of substances is not excluded. The rigid inorganic foam prills of the present invention are produced by entraining a gas into a suspension of one or more layered minerals in a liquid medium to form a foam, and dividing the resulting foam into droplets or wet particles. and removing at least a portion of the liquid medium from the droplets or wet particles formed. The incorporation of gas into the suspension of layered minerals in a liquid medium takes place in the presence of a surfactant, thereby forming a stable wet foam or froth. The term "stable wet foam" means a foamed suspension that does not collapse upon standing or upon removal of liquid from the foam, and in particular does not collapse upon standing within 10 minutes (the height of the foam is substantially reduced). (not) refers to a foamed suspension. As discussed in more detail below, the stability of foamed suspensions is determined primarily by the particular surfactant used for foam formation, as we have found. Although certain surfactants, such as fatty amines and saponins, can form foams, the resulting foams are not stable and collapse within a few minutes; Suspensions are not included within the scope of this invention. The foamed suspension, i.e. the division of the foam into droplets or wet particles, can be achieved in various ways, for example by atomizing the foam through a nozzle or other aperture, by forcing the foam through an aperture in a belt, or by dividing the foam into droplets or wet particles. This can be done by any other known method for dividing into droplets or particulate form. Wet particles or droplets should be at least partially dried before they have a chance to recombine with each other. Dried or partially dried prills can be produced using spray drying equipment. Partially dried prills may be further dried under conditions that prevent their recombination, for example by heating in a single layer or in an agitated bed, such as a fluidized bed. Prills may also be made by forming the foam into a fiber-like extrudate, drying it, and shredding the dried or partially dried material. The density of the rigid foam prills produced by the method of the invention can be determined in various ways, for example by incorporating different amounts of gas into the suspension, by the use of blowing agents and by varying the density of the suspension. can be varied by changing the solids content of. The solids content of the suspension, as well as the type of surfactant used and the temperature at which gas incorporation is carried out, will affect the viscosity of the suspension, but in general an increase in the solids content of the suspension will resulting in an increase in the density of foams produced from
The solids content of the suspension is typically 10-60%, preferably 20-40% by weight of the suspension. Peptizing agents, such as sodium tripolyphosphate, can be added to produce suspensions with high solids content. Suspensions of layered minerals are usually aqueous suspensions, in particular suspensions or dispersions of fines or particles of layered minerals in water, preferably distilled or deionized water. Layered minerals are generally easily suspended or dispersed in water to form suspensions exhibiting colloidal properties. The liquid medium of the suspension can be a mixture of water and a water-miscible solvent such as an alcohol, if desired. However, the liquid medium can be an organic liquid if desired. converting the suspension into a foam;
Subsequent formation into rigid foam prills requires the incorporation of a surfactant into the suspension, which is typically added to the water before or during formation of the suspension. When the layered mineral is vermiculite, the surfactant is blended into the exfoliated vermiculite when the vermiculite is delaminated, so there is no need to add another surfactant. You should understand that. Besides surfactants, other agents such as fillers, compressive strength modifiers, water stability modifiers and flocculants are incorporated into the suspension before, during or after the manufacture of the suspension. be able to. Any surfactant that provides a stable moist foam upon gas incorporation into the suspension can be used. Here, "stable" means that the foam is at least 10
This means that the foam does not collapse upon standing for minutes or upon removing the liquid medium from the foam. Anionic, nonionic or cationic surfactants can be used as long as they provide stable foams. The suitability of a surfactant for use in forming a foam in the process of the invention depends solely on whether the surfactant is capable of forming a wet foam, for example from a suspension with a solids content of 30%, and if so; Determining whether the foam is stable is easily determined by simple experimentation. As a guideline, a wet foam that does not collapse (e.g., no substantial decrease in foam height is observed) upon standing within 10 minutes, preferably within 1 hour, will generally dry the rigid foam prills of the present invention. It is appropriate to give. For the purpose of this test, the test surfactant can be used in any desired amount, ie, at various concentrations, as long as it does not aggregate the foam. Generally, a large amount of surfactant, such as a 2% by weight solution, will give an indication in initial testing whether the surfactant is worth further testing. Surfactants that can be used in low concentrations are preferred, but not essential. A surfactant that provides a stable foam from a suspension of one type of layered mineral may be used to form a suspension of a layered mineral of another type or a suspension of mixed layered minerals, such as a mixture of kaolinite and exfoliated vermiculite. It was found that foams of comparable stability could not be produced from turbid substances. Similarly, it has been observed that a surfactant that cannot produce a stable foam from a suspension of one type of layered mineral can produce a stable foam from a suspension of another type of layered mineral or mixed layered minerals. Served. For example, the surfactant n-butylammonium chloride does not give particularly stable foams from suspensions of kaolinite alone, but it does not give particularly stable foams from suspensions of kaolinite alone, but from suspensions of delaminated vermiculite or from suspensions of kaolinite and delaminated vermiculite. :50 weight ratio mixture gives a stable foam. This must be kept in mind when testing the suitability of surfactants. That is, the test should preferably be carried out with a suspension that is actually desired to be foamed and then dried to produce a rigid foam prill. With respect to surfactants, it has also been recognized that surfactants that form foams most easily do not necessarily provide the most stable foams. Indeed, the inventors have observed that surfactants that generally produce foam only with some difficulty (eg, after foaming the suspension for an extended period of time) tend to produce more stable foams. However, the ease with which a surfactant can generate foam is not conclusive evidence as to the suitability of the surfactant for use in the method of the present invention, and the present invention does not recommend the use of surfactants with low foaming properties. It should be noted that this is not limited to. The amount of surfactant used depends on, for example, the solids content of the suspension, the particular layered mineral used and the surfactant,
It may vary within a wide range depending on the particular foaming technique used and the foaming temperature. As a guideline, the amount of surfactant used typically ranges from 0.1 to
It is 5% by weight. Since the surfactant remains in the rigid foam upon removal of the liquid medium from the foam and its presence is undesirable, the minimum amount compatible with the purpose of producing a stable foam that does not disintegrate upon removal of the liquid medium from the foam. It is preferred to use a surfactant of. Foaming of the suspension can be carried out in various ways, for example by mechanically entraining gas into the suspension by releasing gas or steam into the suspension or by rapid stirring of the suspension. You can do it by doing this. The gas is usually a gas inert to the (aqueous) suspension, such as air, nitrogen, carbon dioxide, hydrocarbons or chlorofluorocarbons. Mechanical entrainment of gas into the suspension can be achieved, for example, by rapid stirring, beating or foaming of the suspension. The release of gas or vapor into the suspension heats the suspension, preferably rapidly heating the gasified liquid medium (or water vapor if the liquid medium is an aqueous medium).
Achieved by releasing bubbles of vapor of a substance (blowing agent) actively incorporated into the suspension as a source of vapor for gas entrainment into the suspension. It is possible. The blowing agent can be a source of hydrocarbons, chlorocarbons, fluorocarbons, chlorofluorocarbons or carbon dioxide, for example. The suspension can be foamed by subjecting it to electromagnetic radiation having a frequency in the range 10 ⁴ Hz to 10 ¹² Hz. The preparation of the suspension and the foaming of the suspension when it does not involve a heating step may conveniently be carried out at room temperature, although higher or lower temperatures can be used if desired. Removal of the liquid medium from wet foam prills formed from foamed suspensions is usually accomplished primarily by evaporation induced by heating of the wet prills. The rate of removal may be controlled, for example, by controlling the temperature or by using a dryer with humidity control means. The density of the rigid foam product made from the foam prills thus obtained is preferably
0.4 g/ml or less, preferably 0.25 g/ml or less,
In particular, it is 0.2 g/ml or less. Typical product densities range from 0.08 to 0.15 g/ml, and may be as high as 0.06 g/ml for particularly lightweight products. The rigid inorganic foam prills of the present invention tend to be soft and exhibit low compressive strength. Although this is related to the particular layered mineral used, the strength of the foam prills can be increased by incorporating compressive strength modifiers therein and/or by heating and sintering the dry foam prills. can be improved. Incorporation of vermiculite lamellae (exfoliated vermiculite) in a mixed layered mineral, for example into a suspension prior to foaming, usually increases the compressive strength of the foam. Except in the case of foam prills consisting solely of vermiculite, high-strength foam prills are dry rigid foam prills obtained by drying a foamed suspension at temperatures up to e.g. 1000°C. Alternatively, it may be obtained by sintering by heating to a higher temperature as the case may be. Sintering of the foam prills results in their densification, but the sintered foam prills still retain their cellular structure and are light. Sintering of foam prills composed of mixtures of vermiculite/other layered minerals depends on the proportion of vermiculite in the prills and the weight loss of the material when heating the foam prills to sintering temperatures. It may result in an increase or decrease or only slight variations in the density of the foam prills. The unsintered rigid foam prills of the present invention composed of layered minerals exhibit little resistance to degradation by liquid water. It is therefore preferred that the foam prills be subjected to a treatment to improve its water stability. For example, a foam prill may be prepared by incorporating a silicone polymer precursor into the foam prill, then creating acidic conditions within the foam prill, and causing polymerization of the precursor under these conditions to form a silicone polymer within the foam prill. Water resistance can be achieved by For example, for an aqueous suspension of kaolinite, sodium methyl siliconate is incorporated into the suspension before or during foaming and the resulting foam prills are exposed to carbon dioxide gas while it is still wet. A silicone polymer can be obtained by treating the silicone with an acidic gas to provide acidic conditions necessary for polymerization of the siliconate. Instead of treating the foam prills with acid gas during drying of the foam prills in the manufacturing process, the foam prills can also be completely dried and then moistened with water to the desired degree. If desired, instead of actively treating with acid gas, the wet foam prills can be left in the air for an extended period of time to absorb carbon dioxide from the air, thereby providing the necessary acidic conditions in the foam prills. You can also.
In the case of sintered foam prills, the silicone polymer added before sintering is destroyed during sintering, so the silicone polymer can impart water resistance after sintering. The relative proportion of the layered minerals in the suspension of the layered mineral mixture and thus in the resulting rigid foam prills may vary within a wide range depending, for example, on the compressive strength and thermal insulation performance required of the rigid foam prills. Can be changed. For example, foam prills contain 90:10 kaolinite or kaolin-containing clay and vermiculite.
It may be contained in a relative weight ratio of 10:90 to 10:90. In general, increasing the relative proportion of delaminated vermiculite in a rigid foam prill not only increases the compressive strength of the prill but also increases its thermal insulation coefficient (K
value) also increases. When the rigid foam prills of the present invention are prills of mixed layered minerals containing delaminated vermiculite, such polyls are formed by incorporating other layered minerals into a suspension of vermiculite lamellae prior to the foaming process thereof. By doing so, you will be guided to your advantage. As described in the above-cited U.S. Pat. No. 4,130,687, suspensions of vermiculite lamellae usually contain a surfactant, such as n-butylammonium chloride, used in the preparation of the suspension. The incorporation of other layered minerals into the suspension may provide both the suspension and the surfactant necessary to produce the desired rigid foam prills. Preferably, the mixed layered mineral foam prills containing vermiculite contain compressive strength and water stability modifiers for rigid foam prills consisting solely of vermiculite. The applicant's own UK patent application discloses that the compressive strength and water stability of vermiculite foams can be improved by incorporating a compressive strength modifier, which is a solid particulate material that exhibits basic reactivity in water.
No. 33723/78 and corresponding European patent application no.
It is described in specification No. 79301577.7. According to that description, the preferred compressive strength and water stability modifier is particulate magnesium oxide, and the vermiculite-containing mixed layered mineral foam prills of the present invention may also include such magnesium oxide. preferable. The compressive strength of such mixed layered mineral foam prills may also be improved by sintering methods such as those described above. The rigid inorganic foam prills of the present invention are useful as intermediates for the production of inorganic foam products, as described above, and such inorganic foam products substantially contain the rigid inorganic foam prills having a cellular structure of the present invention. It is manufactured by assembling the foam into the desired product form, such as a slab or board, with a cellular structure. The term "inorganic foam product" is used here to include foam products in which the true cell structure is not continuous throughout the product. The term therefore refers to foams in which the prills are bonded to each other in the product by adhesive or by mutual attraction, and where there are voids between the prills in the resulting product structure. Includes body products. Furthermore, the term does not exclude the presence of small amounts of organic material, for example up to 20%, present in the prill or actively added, for example as a binder to the prill. Rigid inorganic foam prills of the invention, which may be composed of a single layered mineral or a mixture of two or more layered minerals, such as a mixture of kaolinite and vermiculite Rigid inorganic foam products are heat resistant and thermally insulating materials that are useful in a wide variety of fire protection and thermal insulation applications. Such products are suitable for subsequent processing steps, such as wood, plywood veneers, asbestos, mica, plastics, vermiculite boards (in foam form or made from heat-exfoliated vermiculite particles), It may be manufactured as slab or board material for use in laminate manufacturing processes with sheets of various materials such as vermiculite and polymer impregnated fiberglass scrims. Such laminates form decorative architectural panels useful in the building industry. Slab timber can be used, for example, for sheathing wood, cement or steel building components to provide surrounding fire walls and thermal insulation layers and directly as sheathing, siding and ceiling tiles without lamination with another material. You can also use Although such rigid inorganic foam products can be processed at high temperatures, for example up to 1000° C., for long periods of time without disintegrating, heating at excessively high temperatures and for long periods of time can cause the products to become brittle. The surface of the rigid foam article can be pressed after or during drying to obtain a smooth surface, which can be engraved for decorative effect if desired. Rigid inorganic foam products formed from the foam prills of the present invention may be used in fire doors or fire barriers, if desired in the form of laminates with other materials. Production of the desired rigid foam products from the foam prills of the present invention can be accomplished by gluing the foam prills together. A variety of inorganic and organic adhesives (more preferably inorganic adhesives) can be used to bond the prills together to produce slabs, which can be used for the production of laminates or for use with wood, cement, etc. and for application as coatings or cladding to supports such as steel building components. Slabs up to 10 cm thick or more can be fabricated by joining together the dry foam prills of the invention. Examples of inorganic binders that can be used are phosphoric acid, aqueous phosphate solutions and silicate cements and plasters. Examples of organic binders that can be used are vinyl-
and aqueous emulsions of vinylidene polymers and copolymers. Rigid inorganic foam prills of the present invention, particularly those prills constructed entirely or partially of delaminated vermiculite (vermiculite lamellae), are dry pressed without the need for the use of adhesives or binders. Molding can form a foam product with structural integrity. The foam product obtained by dry pressing of prills is preferably in the form of a laminate in which the product is laminated with layers such as paper or sheets or interposed between two such layers. Although the foam prills of the present invention can thus be converted into desired foam products by dry pressure molding, it is more preferable to moisten or dampen the prills before molding. According to this preferred format:
Rigid foam products are made by applying a solution containing phosphate or silicate ions to foam prills and drying the resulting wet prills while holding them in the desired shape. The phosphate ion-containing solution may be phosphoric acid or a solution of a phosphate salt. Although organic and inorganic phosphates may be used, including complex phosphates, it is preferred to use inorganic phosphates or phosphoric acid since it is desirable that the desired end product be wholly or at least essentially inorganic. A preferred phosphate ion containing solution is orthophosphoric acid. A preferred silicate ion-containing solution is a sodium silicate solution. In one preferred method of manufacturing foam products using the rigid foam prills of the present invention, the foam prills are assembled into the desired product shape, such as a slab or board, and in this form phosphate ions or When dried in the presence of a silicate ion-containing solution, the prills are joined together after drying to obtain a molded article with structural integrity. The phosphoric acid or silicate ion-containing solution may be applied to the prills prior to assembling the individual prills into the desired shape, or may be applied to the assembled prills while they retain the desired shape. Alternatively, the solution forms a dry coating of phosphoric acid, phosphate or silicate on the prills before or after assembling the prills into the desired shape;
It can then be applied onto the prills by wetting the coated prills to form a solution containing phosphate or silicate ions. It is preferred to apply the solution to individual prills before assembling them into the desired shape. It is particularly preferred to form prills with a dry coating of phosphoric acid, phosphates or silicates on the surface. Prills with such a dry coating are easy to store and transport and only require the manufacturer of the shaped article to wet the dry coating before or after assembling the prill into the desired shape. This is because it is only assumed that In practice, it is usually more convenient to wet the individual prills before they are assembled into the desired shape than after they are assembled, and this method allows for controlling the amount of solution applied to the individual prills and It is easier to ensure a uniform concentration of solution throughout the collection of prills. Therefore, according to a preferred embodiment of the present invention,
A rigid foam prill of one or more layered minerals having a dry coating of phosphoric acid, phosphate or silicate on the surface is provided. Such coated prills can be prepared by applying a solution of phosphoric acid or a phosphate or silicate to the prills and drying the prills by evaporating the liquid medium under conditions such that no mutual bonding of the prills occurs from the applied coating. easily manufactured by When the coated prills thus dried are rewetted, a solution containing phosphate ions or silicate ions is again generated on the prills. Drying of the prills may be carried out, for example, by a fluidized bed drying method. The amount of phosphate or silicate ion-containing solution applied to the prill and the ionic concentration of the solution can vary within a wide range, but will affect the physical properties of the shaped article formed from the prill. In particular, the amount and ion concentration of the solution applied to the prills influences the density of the shaped article. Generally, increasing the amount of a particular solution applied to a brill increases the density of the molded article formed from the prill. Similarly, increasing the concentration of ions in the solution increases the density of shaped articles formed from the prills. Other physical properties of the shaped article that are affected by the amount of solution applied to the prill and the ionic concentration are:
At least in the case of phosphate solutions it is the strength of the product. The presence of a peak in the intensity of the product formed from the prill if the amount of phosphate ions (at least in the surface zone of the prill) increases and the amount of solution applied to the prill or its ion concentration increases. It has been observed that an increase in strength beyond the point giving a peak strength results in a decrease in the strength of the product. Although the amount of solution applied to the prills may depend to some extent on the solution application method, the optimal combination of solution application rate and solution concentration for each particular application method can be readily determined by simple testing. It is possible. Application of the solution to the prills may be carried out in any convenient manner, such as by dipping, brushing or rolling, although application by spraying is more preferred. The spraying method has the advantage of being easy to carry out, with control over the amount of solution applied to the prills, and in particular can provide surface coverage with minimal impregnation of the prill structure with the solution. The layered mineral foam prills of the present invention are usually highly porous structures that readily absorb liquids and therefore, unless steps are taken to prevent this absorption, solutions applied to the prills will It will penetrate the quality structure and enter the interior of the prill. Since this phenomenon is undesirable in the present invention from the standpoint of density and thermal conductivity of products made from prills, the spraying method is carried out in a controlled manner to apply the minimum amount of solution necessary to surface coat the prills. It is preferable to adopt In addition to applying the minimum amount of solution necessary to surface coat the prill, a fairly dilute solution of phosphoric acid or phosphate or silicate may be applied to further limit the amount of phosphoric acid, phosphate or silicate applied to the prill. It is preferable to use If I could give you a guideline, it would be 5 to 20.
Preference is given to using solutions with a concentration of 7% to 15% by weight. When prills with a dry coating of the present invention are wetted with water for the production of molded articles, the amount of water added is typically about 60-70% by weight of the prills.
It is. Wet foam prills can be dried at ambient temperature (room temperature), but are typically heated to speed up drying. The temperature of use is not critical and can be heated up to several hundred degrees Celsius if desired. It is generally advantageous to dry the individual wet prills by heating them to high temperatures, for example up to 600°C. The physical properties of the dried coated prills appear to be independent of the temperature used to dry the coated prills. Rigid foam prills of vermiculite lamellae according to the invention are produced by entraining gas into a suspension of vermiculite lamellae to form a foam and the resulting rigid foam is in the form of prills or convertible into prills. It can be produced by removing the liquid medium from the foam under conditions. cutting,
A suitable product form for conversion into prills, for example by cutting with a gas jet, is a foam fiber-like extrudate, which may be cut into prills before drying or after drying. .
Various direct prilling methods may be used, such as spray drying and belt-extrusion, in which the foam is passed through holes in a belt into a fibrous extrudate and the extrudate is cut into prills. Chemical delamination processes of vermiculite for producing suspensions, usually aqueous suspensions, of vermiculite lamellae suitable for conversion into the rigid foam prills of the present invention are known per se, e.g. Patent No. 1016385, Patent No. 1076786 and Patent No. 1119305
and by Baumeister and Hahn in Micron, 7 , 247 (1976). For use in making the rigid foam prills of the present invention, a high proportion of lamellae with a particle size of 5 microns or less are wet classified to remove all particles with a particle size of greater than 50 microns, preferably greater than 20 microns. Preference is given to using a suspension of vermiculite lamellae containing, for example, 40 to 60% by weight. The strength, especially the flexural strength, of molded articles produced by the assembly of the rigid foam prills of the present invention is determined by combining the layers of the bonded prills with paper (e.g. kraft paper or vermiculite paper or glass impregnated with vermiculite). It can be improved by laminating with a surface layer of flexible material such as a fiber scrim) or a metal strip or foil. Although such one or more surface layers may be applied to a preformed foam article from the foam prills using conventional lamination techniques, the surface layer may be applied during manufacture of such foam article. It is more convenient. Therefore, for example,
Slab or board materials are prepared by placing prills with a wet phosphate or silicate coating between the layers of surface layer material, lightly compacting the resulting assembly, and then drying these wet prills to form the center of the foam. It can be manufactured by forming a laminate consisting of a layer and an integrated surface layer. EXAMPLES Next, the production of the rigid inorganic foam prills of the present invention will be explained with reference to examples. In addition, some examples of manufacturing foam products of desired shapes using such prills are shown as reference examples. Example 1 Vermiculite was mixed with refluxed saline solution and refluxed n-
An aqueous suspension of vermiculite lamellae obtained by swelling by successive treatment with an aqueous butylammonium chloride solution and water was milled and then wet classified by removing all particles with a particle size greater than 50 microns. . This suspension is heated in an Oakes mixer or Kenwood food mixer to entrain gas to form a foam and during the foaming operation magnesium oxide powder (based on vermiculite) % by weight) was added. The wet foam was immediately poured onto a perforated "Melinex" belt and "beads" were formed on the underside of the belt by allowing the foam to fall through the holes in the belt. The beads were allowed to stand for a few minutes to harden and partially dry before being removed from the belt by scraping. These beads were then placed on a tray and dried in a heating oven to obtain dry rigid foam prills. By varying the concentration of vermiculite in the suspension, foam prills of various densities were obtained. These prills are approximately cylindrical and have a diameter of 2~
It had an average size of 3 mm, a length of 3 to 5 mm, and a uniform cell structure. Example 2 Density 112 produced according to the method of Example 1
Kg/ ^m3 vermiculite foam prills (20g)
An aqueous solution of concentrated phosphoric acid (5 g) in deionized water (66.5
g) and stirred carefully. Spread the thus moistened prills on a flat drying tray and dry at 60℃ for 16 minutes.
It was dried by heating for a period of time. The existing prill agglomerates were broken up by hand and the fine dust was removed by sieving to obtain dried phosphoric acid coated vermiculite foam prills. Example 3 Density 104 produced according to the method of Example 1
Kg/ ^m3 vermiculite foam prills (50g)
into a laboratory-scale fluidized bed dryer (PR Engineering
For the coating treatment, the prills were placed in a cylindrical fluidized bed with a height of 30 cm and a diameter of 13 cm held in the head of a fluidized bed dryer. and heated to 140°C. Spraying of 2.5M orthophosphoric acid (12 ml) onto the fluidized prills was done using a "Delavan" air atomization siphon nozzle (model 30610-1) at a feed rate of 0.22 cm ³ /sec. Thus, the prill after drying is
Coated with 2.5% by weight orthophosphoric acid. Examples 4-6 Dry rigid ball clay foam prills were made from the following ball clay suspensions.

[Table] “Hymod”/AT is English
This is a ball clay produced in Dorset and sold by China Clay. BSK/L is a North Devon ball clay available from Watson Blake. Hycast/VC is English
This is a ball clay from Devon, commercially available from China Clay. “Forafac” 1157 is Ugine
It is a surfactant containing a C ₇ F ₁₅ group and an amphoteric group, available from Kuhlmann. The water is deionized water. The wet foam formed was converted to dry rigid foam prills by belt extrusion as described in Example 1. In each example, prills with a cell structure and easy to handle were obtained. In another series of tests, the wet foam described above was converted into cellular prills by a spray drying method. The dried prills obtained in all six experiments above were sintered at 1050°C. In both cases, the cell structure of the prills was maintained. Example 7 7.04 Kg of ball clay EWVA, 12.9 Kg of deionized water and 169 ml of “Fuorafutuku” 1157 (0.6% based on clay) were mixed to give a solids content of 35%.
A slurry was prepared. The slurry was foamed for 20 minutes in a Kenwood Chifu food mixer, and the resulting stable wet foam was then converted to foam prills in a conventional spray dryer. The resulting prills were sintered at 1150°C for 5 minutes. Wet foam body is 256
It has a density of Kg/ ^m3 and the sintered prills are 150
It had a density of Kg/ ^m3 . Example 8 Sepiolite (38g) was mixed with deionized water (162g)
and "Fuorafatsuku" 1157 (0.06 g, 0.4% based on the weight of the clay) in a Kenwood Chifu food mixer for 15 minutes to form a stable moist foam. The wet foam with a density of 195 Kg/m ³ was converted into prills of cellular structure according to the belt extrusion method described in Example 1. The obtained prill
Sintered foam prills with a density of 58 Kg/m ³ were obtained by sintering at 1050° C. for 5 minutes. Example 9 An 18.9% slurry of delaminated vermiculite in deionized water (116 g) was added to deionized water (78 g).
and sodium tripolyphosphate (0.5 g). Light grade kaolin clay (67 g), commercially available from BDH Chemicals, was added to the mixture and then mixed and foamed in an Unudtscheff mixer for about 15 minutes. Light grade magnesium oxide powder (3.7 g), commercially available from BDH Chemicals, was then added and the mixture was again mixed and foamed to disperse the powder. The resulting wet foam was converted to foam prills by the belt extrusion method described in Example 1 and the resulting dry prills were sintered at 1050°C for 10 minutes. The density of the sintered prills was 238 Kg/ ^m3 . Example 10 Montmorillonite (50g) was mixed with deionized water (338g).
g) and to the resulting dispersion was added an 18.3% slurry of delaminated vermiculite (137 g) followed by "Fourafac" 1157 (3 g). This mixture was foamed for 1 hour in a Kenwood Chifu mixer to obtain a stable wet foam. This wet foam was converted into dry prills of cellular structure according to the belt extrusion method described in Example 1. The prill obtained after drying at 90℃ is 108
It had a density of Kg/ ^m3 . Example 11 Sodium Montmorillonite (50g - Wyoming Bentonite) and Kaolin Clay (50g -
g) was mixed with deionized water (450 g) in a Kenpachi F mixer until the montmorillonite was completely dispersed. “Fuorafatsuk” 1157
After adding (6 g), the mixture was foamed at maximum speed for 1 hour to form a stable wet foam. Dry foam prills produced from the wet foam by the belt extrusion method described in Example 1 were then heated at 1050°C for 10
After sintering for minutes, the prills had a density of 118 Kg/m ³ . Example 12 Sodium montmorillonite (Wyoming bentonite - 50 g) and deionized water (450 g) were stirred in a Kenwood Chief mixer until the montmorillonite was completely dispersed. 1157 (6 g) was added and the mixture was then whipped at maximum speed for about 1 hour to produce a stable wet foam. Dry foam prills were produced from this wet foam by the belt extrusion method of Example 1, and then
Sintered at 1000℃ for 10 minutes. Sintered prill is 110Kg/
It had a density of m ³ . Reference Example 1 A board measuring 15 cm x 15 cm x 2.5 cm was produced from a dry foam prill of approximately spherical delaminated vermiculite having a diameter of 3 mm produced as described in Example 1. The prills used had a true density of 5 Kg/m ³ and a packing density of 45 Kg/m ³ . Dry prills (22 g) were placed in a 15 cm x 15 cm x 2.5 cm steel mold, and the prill assembly was compressed using a steel plate with a force of 15 Kg/m ³ . Pressure was applied until the volume of the prill assembly was reduced to approximately 1/2. The resulting product is essentially a board with a cellular structure, with a density of 90Kg/m ³ ,
It had a bending strength of 30KN/ ^m2 and a compressive strength of 100KN/ ^m2 . The board was extruded from the mold and its two major surfaces were coated with a 35% aqueous solution of sodium silicate. A glass fiber scrim weighing 50 g/m ³ was pressed onto these coated surfaces, and the resulting laminate was dried in a heating oven for 2 hours. This laminate is 95
Density of Kg/ ^m3 , bending strength of 300KN/ ^m2 and
It had a compressive strength of 150KN/ ^m2 . The thermal conductivity of the laminate, measured according to British Standard (BS) 874, was 0.056. Reference Example 2 Board material measuring 15 cm x 15 cm x 2.5 cm was produced as described in Reference Example 1, except that the prills were moistened with deionized water (44 g) before being charged into the mold. . The board material obtained essentially had a cellular structure and its density was 90 Kg/m ³ . Furthermore, this board has a bending strength of 60KN/ ^m2 and
It had a compressive strength of 110KN/ ^m2 . This board was laminated with a glass fiber scrim as described in Reference Example 1. The dry laminate has a density of 95Kg/ ^m3 ,
It had a bending strength of 400KN/ ^m2 and a compressive strength of 130KN/ ^m2 . Reference Example 3 The dry phosphoric acid coated foam prills (8 g) obtained in Example 2 were thoroughly mixed with deionized water (16 g) and the thus moistened prills were made into 4.35 mm diameter prills lined with "Melinex" plastic.
The mixture was lightly filled into two cylindrical tubes with a height of 2.0 cm and a height of 2.0 cm using a knife-shaped spatula. After skimming the flat upper and lower surfaces of the resulting prill assemblies with a spatula to give a smooth surface finish, these cylindrical tubes were
The mixture was heated for 4 hours in a heating oven at .degree. The cylindrical tubes were removed from the furnace and the cylindrical foams were extracted from the tubes and their compressive strength (10% compression) was immediately measured using a Houndsfield tensiometer. This product contains 20% by weight of phosphoric acid binder, has a density (average of two samples) of 206 Kg/m ² and a compressive strength of
It was 274.8KN/ ^m2 . Cylindrical foam articles were made exactly as above from the same foam prills, except that the phosphoric acid binder content was 10% by weight instead of 20%.
The density of this product (average of 2 samples) is 154Kg/
m ³ , and the compressive strength was 126.4KN/m ² . Reference Example 4 The dry phosphoric acid coated foam prills (8 g) obtained in Example 3 were formed into cylindrical foam articles in the manner described in Reference Example 3 and tested. The product obtained has a density of 127 Kg/ ^m3 (average of two samples) and
It had a compressive strength of 386KN/ ^m2 . Reference Example 5 A board material was manufactured from the foam prills manufactured in each of Examples 4 to 12 by the following method. The dry foam prill (5) was placed in the rotating drum of the spraying device and sprayed with a predetermined amount of binder solution. The amount of binder used was selected so that the density of the final dry board ranged from 110 to 230 Kg/m ³ . Wet prill 30cm x 30cm
The mixture was transferred to a 4 cm x 4 cm mold and compressed until the volume was reduced to 1/2 to obtain a 30 cm x 30 cm x 2 cm board. The obtained board was dried in a heating oven at 60°C. Boards made with silicate binders (see below) were further heated to 200°C. In all cases, the boards obtained had a rigid, essentially cellular structure. The following two types of binders were used when manufacturing boards from the prills manufactured in each of the above examples. (1) A 60% aqueous dispersion of a copolymer of vinyl chloride, vinylidene chloride and alkyl methacrylate (“Haloflex” 202 from ICI)
commercially available as). (2) 40% aqueous solution of sodium silicate. The boards made with the "Haloflex" binder showed better bending strength in all cases than the boards made with the sodium silicate binder. Each of the boards produced as described above was pressed against a glass fiber scrim as described in Reference Example 1 to form a laminate, which was dried in a heating oven at 60°C. The adhesive used in the production of this laminate varied depending on the binder used in the production of the boards from the prills, i.e. for boards with "Haloflex" binder, "Haloflex"dispersion; On the other hand, for board materials using sodium silicate binders, chemically delaminated vermiculite
An 18% slurry was used. All of the resulting laminates exhibited improved flexural and compressive strength compared to non-laminated boards.

Claims (1)

[Scope of Claims] 1. A prill of a hard inorganic foam having a cell structure and composed of one or more layered minerals. 2. The prill according to claim 1, wherein the layered mineral is exfoliated vermiculite. 3. The prill according to claim 1, wherein the layered mineral is kaolinite or kaolin-containing clay. 4. The prill according to claim 1, wherein the layered mineral is montmorillonite. 5. The prill according to claim 1, wherein the layered mineral is sepiolite. 6. The prill according to claim 1, wherein the layered minerals are vermiculite and kaolinite. 7. The prill according to claim 1, wherein the layered mineral is exfoliated vermiculite and kaolinite. 8. The prill according to any one of claims 1 to 7, which is coated with a binder or adhesive. 9. A prill according to any one of claims 1 to 8 having a density of less than 0.4 g/ml. 10. A prill according to claim 3 having a density of less than 0.2 g/ml. 11. Foaming a suspension of one or more layered minerals in a liquid medium to form a stable, moist foam, and shaping the moist foam to form droplets or fiber-like extrudates. and removing at least a portion of the liquid medium from these droplets or extrudates. 12. The method for producing prills according to claim 11, wherein the layered mineral is selected from montmorillonite and sepiolite. 13. A method for producing a prill according to claim 11, wherein the layered mineral is composed of exfoliated vermiculite and contains in its suspension a compressive strength and water stability improver for the resulting foam. . 14. The method for producing prills according to claim 13, wherein the compressive strength and water stability improver is granular magnesium oxide. 15. Production of a prill according to claim 11, in which the layered mineral is made of something other than vermiculite with delaminated layers and the resulting hard inorganic foam is sintered to improve its compressive strength and water stability. Law. 16. The method of manufacturing prills according to claim 15, wherein the foam is heated to a temperature of up to 1200° C. to sinter it.